When is your fertile window?

You might be surprised to learn it’s only possible to get pregnant on a small number of days in your cycle. It’s called the ‘fertile window’ and it starts around 10 days into your cycle, lasting for five days plus your ovulation day.  

If you’re hoping to conceive as soon as possible, here’s what our fertility experts want you to know about your fertile window, including tips on tracking your cycle and the best time to have sex to increase the chances of pregnancy.   

This article covers: 

• What your fertile window is 

• Ways to track ovulation 

• How accurate are ovulation trackers?  

• Tips for conceiving during your fertile window 

How do you track your ovulation and fertile days? 

Calculating your fertile window can be challenging. On average, ovulation happens on day 15 of the cycle, but 1 in 2 women have cycles that vary by five or more days each month. Simply counting the days (calendar technique) may only be accurate if you have a very regular cycle.  

There are several techniques to help track ovulation. If you’re aiming for pregnancy, you’ll need to know which methods are predictive, as some approaches can only confirm that ovulation already happened.   

Ovulation tracking methods include: 

• Ovulation prediction kits (OPK) – a digital or manual dipstick that detects a surge of luteinising hormone (LH) in the urine to predict ovulation 

• Cervical mucus – manually checking your discharge to look for signs that ovulation is about to take place 

• Ovulation tracking apps – an app uses the calendar method, which aims to predict ovulation based on data you input about your cycle 

• Basal body temperature – monitoring the body temperature to look for a small rise, which indicates that ovulation happened 

• Progesterone kits – monitoring a rise of progesterone in the blood or urine to confirm ovulation took place 

If you want to accurately predict your ovulation before it happens, you’ll need to use an ovulation prediction kit or the cervical mucus method. Cycle-tracking apps also aim to predict ovulation, but these are widely considered to be less accurate due to variations in cycle lengths.   

Ovulation prediction kits (OPKs) 

OPKs are an at-home tool that come at a range of price points. More expensive kits aren’t necessarily more accurate, but they might be easier to use. They look similar to a pregnancy test and detect a large increase of LH in the urine. 

The day before ovulation, the brain sends out a large surge of LH, the hormone that triggers the ovaries to release an egg. Experts recommend using an OPK at the same time every day (10am to 2 pm), starting around 10 days after the first day of your period.  

Although the LH surge is released from the brain early in the morning, hormones take time to cross the blood-brain barrier, get into the bloodstream, and then filter through the kidneys into the urine.  

When you test positive, it means your ovulation is predicted to happen the next day. The day of your LH surge and the day after are good times to have sex if you’re planning a pregnancy.  

OPKs might not be the best method for you if: 

• You have PCOS – people with PCOS tend to have naturally high levels of LH, and so an OPK can give a false positive result 
   

• You have very irregular cycles – it’s recommended that you consult with a doctor if you’re trying to get pregnant whilst experiencing irregular cycles. Using OPKs can become expensive due to challenges in finding your ovulation day  

The cervical mucus method  

Checking your cervical mucus could be considered the ‘old fashioned’ technique for monitoring your cycle. It’s free and simple to do at home.  

Throughout your menstrual cycle, the consistency of your cervical mucus changes. As your body gets ready to ovulate, your discharge becomes clear, slippery, and wetter. This helps sperm swim into the cervix to reach the fallopian tubes.  

When you’re outside your fertile window, your cervical mucus is likely to be thicker, yellow or white, and may feel more like a paste.  

To check your cervical mucus, insert a clean finger inside the vagina and scoop out some of the discharge. If it’s clear and slippery, you’re likely to be in your fertile window. If it’s very wet and stretches between your fingers, you may be ovulating.  

How can you improve your chances of getting pregnant during your fertile window?

On average, your chances of getting pregnant range from 1 in 10 at the start of your fertile window, to up to 1 in 3 on the day of ovulation, according to widely quoted studies.  
 
The main way to increase your chances of pregnancy is to have unprotected sex at least a couple of times during your fertile window, with semen entering the vagina. But beyond the basics, what else can you do? 

• Consider having regular sex throughout your cycle – no matter which method you use, ovulation prediction isn’t always accurate, so the safest bet may be to have sex every 2 to 3 days throughout the cycle (excluding menstruation) 

• Quit smoking and reduce alcohol intake – a healthy lifestyle helps optimal sperm and egg production, and making these changes can offer a relatively fast boost to your fertility  

• Don’t abstain from ejaculation – there’s no need to ‘save up’ your sperm because ejaculating at least every few days is recommended to flush out dead sperm cells (up to a maximum of once a day) 

• Set realistic goals – couples can feel the pressure when it comes to having frequent sex around ovulation, and it’s better to have an achievable plan rather than feeling stressed and burnt out by an agenda that doesn’t suit your sex drive 
   

• Use whichever position you prefer – the fluid that comes out of the vagina after sex is mostly just semen because healthy sperm quickly swims into the cervix, so most experts would advise that no special position is required for pregnancy 
   

• Consider a fertility assessment – if you’ve been trying for over a year, are over the age of 35, or have very irregular periods, it’s recommended to see a fertility specialist to find out whether you might need extra help conceiving  

Learn more about ways to naturally increase your fertility at home, using simple lifestyle changes to help support healthy egg and sperm production.